Method of manufacturing an electron tube



June 9, 1959 H. J. KocH 2,889,670

METHOD OF MANUFACTURING AN ELECTRON TUBE Filed April 21. 1954 2Sheets-Sheet 1 IN VEN TOR.

HENRY J. KOCH ATTOE/VEK June 9, 1959 J KOCH 2,889,670

METHOD OF MANUFACTURING AN ELECTRON TUBE Filed April 21, 1954 2Sheets-Sheet 2 INVENTOR. f/E/VEY J KOCH United States PatentO METHOD OFMANUFACTURING AN ELECTRON TUBE Henry J. Koch, Belleville, NJ, assignorto National Union Radio Corporation, Hatboro, Pa, a corporation ofDelaware, now by change of name to National Union Electric CorporationApplication April 21, 1954, Serial No. 424,665

3 Claims. (Cl. 53-9) This invention relates to electron tubes and moreespecially it relates to tubes of the so-called miniature kind.

A principal object is to produce a novel form of tippedoff exhausttubulation for electron tubes and the like.

Another object is to provide a novel construction of glass header with atipped-off exhaust tubulation which is recessed within the externalsurface of the header.

A feature of the invention relates to an electron tube or similar devicehaving a glass header or base through which contact prongs or lead-insproject internally, and having a recess in its external face withinwhich is seated a bent tipped-off exhaust tubulation.

A further feature relates to the novel organization, arrangement andrelative location of parts which cooperate to provide an improvedelectron tube of the type having a tipped-off exhaust tubulation in thebase thereof.

- Other features and advantages will be apparent after a considerationof the following detailed descriptions and the appended claims.

In the drawing which shows, by way of example, one preferred embodiment,

Fig. l is a top-plan view of an electron tube header or base accordingto the invention, prior to assembly in the finished tube.

Fig. 2 is a sectional view of Fig. 1, taken along the line 22 thereof.

Fig. 3 is a sectional view of the header of Fig. 1 having an exhausttubulation attached thereto.

Fig. 4 is a schematic plan view of a conventional tube assembly andexhaust machine for manufacturing the mbe according to the invention.

Fig. 5 is a detailed view explaining one step in the operation of themachine of Fig. 4 according to the invention.

Fig. 6 is a view similar to Fig. 5, showing a succeeding step in theoperation of the machine.

Fig. 7 is a detailed view, partly in section, of a finished tubeaccording to the invention.

In present day electron tubes of the so-called miniature type, the tubeconsists of a flat button-like glass header through which are directlysealed the contact prongs or lead-in members and this header has sealedthereto the conventional glass bulb or envelope. In such tubes, noseparate supporting base is necessary since the contact prongs emergedirectly from the glass header. In order to exhaust the air or othergases within the tube, prior to scaling off, it is necessary to providethe tube With a conventional exhaust tubulation. In certain types oftubes, this exhaust tubulation is attached to the upper end of the bulband when the bulb has been exhausted, the tubulation is tipped off inthe conventional way to leave a vertically extending tip at the top ofthe tube, which presents a source of trouble in that it is likely to bebroken off at any time and thus destroy the usefulness of the tube. Ithas not been found practicable heretofore to manufacture such tubes withthe exhaust tubulation at the base of the tube because it is impossibleto tip off this tubulation so that the extreme tip thereof does not2,889,670 Patented June 9, 1959 extend beyond the external face of thebase. If the exhaust tubulation does extend below the base, thepluggingin of the tube into the conventional tube socket would cause thetip of the exhaust tubulation to be subject to breakage.

In accordance with the present invention, I have devised a method ofmaking a tube of the so-called miniature type, wherein the exhausttubulation is attached to the glass header or base and is processed sothat in the final tube the exhaust tubulation does not extend below theexternal surface of the glass base or header.

For the purpose of explaining the invention, there is shown in Figs. 1and 2, a glass header or base 10, through which are sealed in circulararray the usual rigid plug-in prongs or lead-ins 11. In the standardminiature tube the header has nine such lead-ins sealed directlytherethrough so that the externally projecting portions 12 form theplug-in connector members for making contact with the usual nine-pintube socket (not shown). Heretofore, it has been customary to make thebottom or external surface 13 of the glass header completely flat.However, in accordance with one feature of the invention, the header 10is provided with a central recess 14 to which the conventional elongatedglass tubulation 15 (Fig. 3) can be united by conventional machinery soas to provide a continuous exhaust path through the tubulation into thecontents of the bulb 16 which is to be sealed to the peripheral marginof header 10 in the conventional way.

Merely for purposes of explanation, there is shown in Fig. 4, inschematic plan view, any well-known form of tube making machine which iswell known in the art, for example a Sealex machine. Such machinecomprises a rotatable platform 17 carrying a plurality of headsindicated schematically by the numerals 18-24. The platform 17 in thewell-known manner, is adapted to be indexed or rotated intermittently inthe direction of the arrow and also the heads 18-24 are arranged to beindividually rotated in front of the usual gas jets or sealing fireslocated at respective stages. Merely for illustrative purposes, one ofthe rotatable heads 18 is shown adjacent the loading position whereinthe operator inserts into the conventional stem holder the unitconsisting of the header 1t? and the exhaust tubulation 15 shown in Fig.3. Each of the heads is also provided with the conventional bulb holderindicated schematically in Figs. 5 and 6 by the numeral 25.

When the operator has loaded a tubulated stem and bulb into the head 18,the platform 17 is indexed counterclockwise to the next position wherethe bulb 16 has its lower end sealed to the peripheral margin of theglass header it) in the conventional way. The platform 17 is thenindexed to the exhaust position where the tubulation 15 is connected toany well-known form of vacuum pump so as to exhaust the air and othergases from Within the sealed bulb. After the bulb has thus beenevacuated, the platform 17 is indexed to bring the evacuated bulb intothe tipping-off position wherein the exhaust tubulation 15 is melted andpinched as closely adjacent to the bottom face of the header 10 aspossible. It has not been found practicable heretofore to effect thistipping-off without having some of the exhaust tubulation 15 projectbelow the surface of the header 10 as illustrated in Fig. 5.

In accordance with the present invention, the platform 17 is indexed toa tip-recessing position wherein the tippedoff bulb with the downwardlyprojecting tipped-01f tubulation 15 is brought into registry with aspecial gas flame 26 which softens the tubulation 15. When thetubulation has thus been softened, the gas flame 26 is removed and atool 27 is forced upwardly into contact with the softened tubulation asshown in Fig. 6, causing that tubulation to be bent out of the verticalposition until it is Since the center of the stem or header 10 has beeni heated to effect the bending of the tubulation 1S, undesirable strainsmay exist in that central region which may render it necessary to annealthe glass header. For this purpose, the platform 17 may be indexed tothe annealing position at which the tipped-off and exhausted tube can besubjected to a suitable annealing temperature, for example 430 C. in thecase of soft glass, and then allowed to cool down uniformly to about 100C. During this annealing stage, if it is found that gases are evolvedwithin the tube, a suitable getter of known construction within the tubecan be flashed in the well-known manner so as to pick up these releasedgases. The platform 17 can then be indexed to the final or unloadingposition from which the completed tipped-01f exhausted tube can be removed. The finished tube then has the appearance shown in Fig. 7,wherein the upper end of the bulb 16 is completely smooth and free fromthe usual tipped-01f exhaust tubulation.

While the invention has been described in connection with the sealingand tipping-01f of an electron tube, it will be understood, of course,that it is equally well applicable to the sealing and tipping-01f ofother similar devices such as electric lamps, vacuum switches, gas tubesor any device having an evacuated tipped-01f bulb with contact prongsintegrally sealed through the base or header ing an exhaust tubulationto a preformed recessed portion in the external face of said flattenedbutton-like glass header, softening and tipping said tubulation adjacentsaid header with the tip extending outwardly beyond said header, andpressing back said tip while in a softened state until it is completelyhoused within said recess and is completely external to said header.

2. The method of making an electron tube and the like, which comprises,sealing a relatively thin-walled glass bulb to a relatively thick headerof the button-like kind having an external preformed recess with acentral exhaust tubulation extending therefrom, evacuating the bulbthrough said header, tipping off the tabulation adjacent said header,reheating the tipped-off tubulation to render it plastic, and bendingthe plastic tipped-01f tubulation back into said recess within thebottom of said header, the tubulation being completely external to saidbulb and being substantially free from any portion extending externallybeyond said header.

3. The method of tipping off an electron tube of the kind having arelatively thin-walled bulb portion and a relatively thick button-likeheader having a preformed external recess carrying an external exhausttubulation, which comprises, melting the tubulation adjacent the headerto form a softened tip which extends outwardly from said recess, andsubjecting the softened tip to a mechanical flattening force to flattenit and to press the flattened portion into said recess and withoutchanging the shape of said bulb portion.

References Cited in the file of this patent UNlTED STATES PA'YENT S793,211 McDonnell June 27, 1905 1,056,971 Coleman Mar. 25, 19131,398,033 Maurer Nov. 22, 1921 1,982,317 Nouromtseff Nov. 27, 19342,169,112 Scott et al Aug. 8, 1939 2,200,911 Bowie May 14, 19402,229,436 Beggs Jan. 21, 1941 2,262,760 Gardner et al Nov. 18, 19412,400,635 Eitel May 21, 1946 2,401,638 Herzog et al June 4, 19462,464,765 Palmer Mar. 15, 1949

